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Exhaust Theory for the
Masses We see
it every day. A guy who thinks he can make his standard car look racy
by adding a muffler tip with a diameter as big as a man hole's. Some
of these tips hang way off the car. Shouldn't they have a red flag
hanging from that tip or something? Or maybe a sign saying "Long
Vehicle". Am I the only one that finds this to look most obscene and
disturbing? Anyway, on with the real story. I just had to get that off
my chest.
Exhaust theory has probably been the most misunderstood aspect of
performance modifications. It is the general consensus in Barbados
that the bigger the bore (and tip!) the more horses you get. NOT
NECESSARILY. Let's look at this exhaust system from the time it leaves
the engine (which incidentally is where your exhaust system starts).
MANIFOLD/EXTRACTOR
| There
are 2 terms used to identify the tool that takes exhaust gases
from the engine - the manifold and the header (better known in
Barbados as an extractor). Manifolds are basically the useless
pieces of metal that come with the car. Pretty standard looking
but does its job well, if performance isn't a priority.
Unfortunately they are restrictive when it comes to airflow. The
extractor/header is a performance upgrade that allows the engine
the breathe a lot better. On a 4 cylinder engine there are
basically 2 types of headers: 4-2-1 and 4-1. The 4-2-1 setup
features 4 individual pipes leading from the engine which go to 2
pipes and finally 1 pipe leading to the catalytic converter. This
setup is designed to improve low end torque. The 4-1 design
features 4 pipes which go straight into 1 pipe going to the cat.
This improves mid to high end power. When buying a header,
remember to look for one with short pipes of a large diameter.
Long pipes of a short diameter give better fuel economy and a bit
easier drivability. |
DC SPORTS 4-2-1
design
DC SPORTS 4-1
design
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CATALYTIC
CONVERTER
This device is simply used to clean up the spent gases from the engine
to make them environmentally friendly. The debate continues as to
whether taking out the cat gives more horses. If you don't give a damn
about the environment (shame on you) you can remove it but modern cats
are pretty efficient so any gains will be very marginal.
RESONATOR &
SILENCER
These are located somewhere along the exhaust pipe and are used to
cancel out much of the vibration and some of the noise the engine
produces. A straight pipe design without these devices can improve
exhaust flow (hence increased performance) but you may have to drive
around with earplugs. Turbocharged cars are capable of having an
exhaust system void of a resonator or silencer (sometimes even the
muffler) because the turbo "eats up" a lot of the sound produced.
That's why they are so quiet.
PIPE DIAMETER
So you've bought your 20-valve Levin or your 1600 Integra and you are
ready to tear down. You decide to get an exhaust system with a 3" bore
and figure you can get 20 more horses! The only thing you will be
doing is scraping the bumps and trying to avoid the speed humps.
Installing a system with a bore over 2.5" on a 1600 NA engine is a
waste of time. 2"-2.5" is enough, unless you have a bigger engine or
install a charger. A 3" bore is adequate for an engine that produces
about 250-350bhp. 4" bores would be good for a 400+bhp setup. Mandrel
bent piping allows gases to flow better in the curves of the exhaust
pipe as opposed to press bent piping. The disadvantage is that it's
more expensive. In case you don't know, mandrel bending is a process
that allows the diameter of the pipe to be maintained even through the
bend. With pressed bent piping, the diameter of the pipe is smaller in
the bend. This can cause turbulence of the air flow. As a result, some
efficiency will be lost.
MUFFLER
 Now this is
what it's all about. You don't give a damn that your exhaust bore is
only 1.5 inches. No one can see that. No one can even see the stock
manifold under the hood. All they need to see is your shiny new
stainless steel muffler. It's extremely loud and naturally the bore
size of the tip is 4 inches. You wanted a bigger bore but somehow you
just couldn't find a muffler with one. You must have gained 25 horses
alone with this barrel. Incorrect. Well, at least you sound like
you're going fast. The best way to gain horses is to use no muffler at
all! I wouldn't suggest this if you aren't running a turbocharger
though. When buying a muffler make sure you decide on what you want
before you face the store. Do you want a quiet car with a nice deep
sound or would you rather a loud raspy sound? Mufflers with a small
barrel tend to be louder than big barrel mufflers. Twin pipes, square
tip, round tip? Make sure you get a barrel that suits your car. You
should also make sure you have good ground clearance after
installation.
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